A gas that behaves as randomly moving, non-interacting molecules. This allows a simplified equation of state.

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How is the work done by a system turned into internal energy according to the first law of thermodynamics?

I have several questions about the first law of thermodynamics: When we have a force over a piston of a recipient with an ideal gas inside and that piston moves, we have work associated with that. ...
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0answers
31 views

Thermodynamics - Gas Laws [on hold]

Can anybody please help with the following problem? The compression ratio of an engine is 16:1. The volume of air in the cylinder is $0.5 \,\mathrm{litres}$ at a temperature of $30 ...
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0answers
14 views

plasma and infinite acceleration

I am trying to set up a simulation of particles (they are not any particular kinds of particles, they are just points that repel each other). All the particles repel each other through the inverse ...
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1answer
37 views

Zero volume at zero Kelvin

Why does the volume of a gas become zero at 0 Kelvin? Can a Bose Einstein condensate be considered as matter? (I mean the volume becomes zero)
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0answers
13 views

Finding the temperature needed to have speed of gas atom equal to Ve [on hold]

We are given n moles of a monatomic gas Argon Molar mass 6.4*10^-26. Pressure equal to 101300 pascals. Temperature = 300 K Need to find the average speed of one of the atom of the gas. Secondly I ...
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1answer
40 views

To find average speed of gas molecule when the temperature is incresed

We are given moles of gas let say $n$. Temperature is increased from $T_1$ to $T_2$. Volume is held constant at $V_0$. We need to find the average speed of gas molecule when the temperature $T_2$ is ...
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1answer
25 views

Amount of unknown parameters in compressible Euler equations

I'm looking at this page for the compressible Euler equations. To me it seems, in the 1-dimensional case, there should be 3 unknowns: density, velocity, and pressure. This is because the energy $E$ ...
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2answers
10k views

Calculating work done on an ideal gas

I am trying to calculate the work done on an ideal gas in a piston set up where temperature is kept constant. I am given the volume, pressure and temperature. I know from Boyle's law that volume is ...
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1answer
17 views

Thermodynamics Work Done At constant pressure and charles law

If we fix a piston in the mouth of a cylindrical container in such a way that the piston settles when the pressure from outside the piston is equal to that of the gas within the container, and ...
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1answer
24 views

Water and steam ratio

What is the relationship between the water and steam? I've read that 1 mililiter of water evaporate to 1.6 LITER of steam. Is that true?
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1answer
11 views

Viscosity for steam in the Reynolds number

In calculating the Reynolds number for a flow of steam in a pipe, this is the general formula I am trying to use: $$Re=\frac{\rho d v}{\mu}$$ with density $\rho$, pipe diameter $d$, flow steam $v$ ...
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0answers
22 views

Modelling the diffusion of gas in a container with non uniform temperature

I want to model diffusion of a gas (e.g. water vapor diffusion in air) in a container with a temperature gradient. One side of the container has a hole, but for simplicity of boundary conditions I can ...
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1answer
21 views

On the definition of the compressibility`

The compressibility factor for a real gas can be defined in two equivalent ways, $$Z = \frac{V_{measured}}{V_{ideal}} \equiv \frac{p_mV_m}{nRT} $$ where the subscripts $m$ stand for measured ...
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0answers
12 views

Temperature Frequency relationship for gas?

I am getting something like this T (C) = Constant*log(Frequency) I do not have background of physics and I am wondering, if there is any formula which can explain the physics behind it? Something ...
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0answers
20 views

Timescales for isothermal processes

My understanding is that processes in ideal gases need to take place over relatively long timescales to be idealised as "isothermal" such that the gas temperature can be assumed not to change. For ...
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1answer
3k views

Calculate mass of air in a tyre from pressure

How can one calculate the mass of air inside a tyre, given a particular tyre size; a pressure, in $kPa = \frac{1000kg}{m\cdot s^2}$; and assuming room temperature, and normal air composition? I can't ...
2
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3answers
357 views

Conversion of ideal gas to real gas via $Z$ compression factor

The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
2
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3answers
220 views

Why does the system move until equal temperatures are obtained?

In my college level thermodynamics class, the teacher gave us the example of a closed system which consisted of a box thermally insulated. A piston fully divides the box in two parts, and each is ...
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1answer
106 views

Is the Maxwell distribution a solution of the Boltzmann equation?

I am studying about the Boltzmann Equation for non equilibrium rarefied gases (dilute gases to be more specific): $$\frac{\partial f}{\partial t}+\pmb{v}\cdot\nabla_{\pmb{x}}f=Q(f,f)$$ My question is ...
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2answers
5k views

Work Done by an Adiabatic Expansion

I am given the information that a parcel of air expands adiabatically (no exchange of heat between parcel and its surroundings) to five times its original volume, and its initial temperature is 20° C. ...
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1answer
172 views

What happens in a gas of magnets?

This SMBC comic asks what happens if you make a gas of magnetic particles: I was wondering whether anyone has run into actual examples of this or something like it. A classical example similar to ...
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1answer
70 views

Calculating the entropy of a monatomic ideal gas

I am looking at the start of the consider how to calculate the entropy of a monatomic ideal gas. We need to determine the number of microstates in $E \leq \mathcal{H}(\Gamma) \leq E+\Delta$. The ...
3
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1answer
55 views

Thermodynamics of expanding nitrogen bubble as it rises in water

Problem An air bubble is released from a nitrogen tank 20 meters under water. The bubble has a radius of 1 mm. What will be the radius of the bubble when it reaches the surface? My Questions Is it ...
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2answers
44 views

physical meaning of pressure derivatives

Is there any physical meaning of the first and second derivatives of pressure with respect to time? If this helps, I am considering ideal gases.
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69 views

How does a heated constant volume flow behave, for an expanding flow tube leading into the free atmosphere

I have a helium gas flow with a flow rate that has been set to a constant value ($0.3\,m^3/h$). It's streaming upwards in the picture, and beyond the upper big red dot position, it meets the ...
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2answers
79 views

Why is most probable speed not equal to rms speed for an ideal gas?

The rms speed of ideal gas is $$\mathit{v_{rms}} = \sqrt{\dfrac{3RT}{M}}.$$ The most probable speed is the speed where $\dfrac{dP(\mathit {v})}{dv} =0$ where $P(\mathit{v})$ is the probability ...
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1answer
49 views

Is the gas constant really a constant?

For ideal gases we have $$ C_p-C_v=R $$ now the left hand side of this equation is temperature dependent, so how is it possible that gas constant $R$ is temperature independent?
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1answer
653 views

How fast will sublimed dry ice mix with air?

I saw this photo and wondered: Will the CO2 stay mostly in a layer on the floor with the rest of the atmosphere resting on top, or will it quickly diffuse throughout the room? This lab is probably ...
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0answers
14 views

Doubt about Hard Sphere Model

I couldn't find a proper answer about this question: if I have a gas formed by a single species (ex: biatomic gas like O2), what is the diameter $\sigma$ of the relative hard sphere model? Is it the ...
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1answer
31 views

What assumptions can be made using a $pV$ diagram?

In this question I am asked to find the volume of a gas at $V_3$ I have some parts that am not clear on. Is it reasonable to assume the temperature at $3$ is $657^{\circ}C$ Work is done by the ...
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2answers
758 views

How does a gas of particles with uniform speed reach the Maxwell-Boltzmann distribution?

Take an empty container and fill it with $N$ gas particles (ideally a monoatomic gas), each having the same kinetic energy $E$, then isolate the container. Since initially the speeds don't follow the ...
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1answer
48 views

Decrease in system pressure do to gas dissolution?

A system of fixed volume contains two fluids as illustrated in the figure below, in equal volumes. Their pressures are both equal and high (much greater than atmospheric pressure). Initially the ...
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3answers
789 views

Temperature change inside pressure chamber

Let's say there is a pressure chamber with some sort of sample / specimen (e.g. protein crystal) in it. Now I apply a certain amount of gas pressure, e.g. 10 or 20 atm. Let's say I use xenon as a gas. ...
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0answers
28 views

Necessity of infinitesimal steps for reversible processes

Is there a mathematical proof for why a reversible process is one that has many infinitesimal equilibrium steps, rather than fewer large steps? Maybe something along the lines of this?: ...
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2answers
712 views

Entropy and chemical potential of an ideal gas

I am reading Schroeder's book "Thermal Physics". One calculation in the text was not quite clear to me. The entropy of an ideal gas is given by the Sackur-Tetrode equation: $$ ...
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1answer
41 views

What's wrong with this derivation of pressure-temperature for an ideal gas?

The pressure temperature relationship for an ideal gas, known as Amontons law or Gay Lussac's law should be obtainable from Boyle's and Charles's laws. I did the following. For a given sample ...
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4answers
125 views

Relation between temperature and pressure?

I was just working on a special question but I ignored the effect of temperature on it and now it becomes very important to me. What is the relation between Pressure and Temperature? Suppose we ...
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6answers
1k views

Gay-Lussac's Law & the Patriots

This may be a question better suited for xkcd what if? section...but here goes: with all the hoopla around the patriots / colts game and allegations of cheating by deflating footballs, I've read/heard ...
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1answer
40 views

Can covering an open container with a lid change the pressure of gas in the container?

Consider an open container at standard atmospheric pressure. Now a lid is placed over it, in the most normal way possible. Would the pressure of gas inside the container be the same as the standard ...
3
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1answer
83 views

Calculation of the efficiency of a Carnot engine for photon gas

I am working on a problem considering the Carnot cycle for a photon gas. The cycle has two isothermic processes at $T_{H}$ and $T_{C}$ and two adiabatic processes. The entropy of the photon gas is ...
0
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1answer
38 views

Gas compressed and cooled

If a certain amount of a gas is compressed into a cylinder by the action of a piston that reduces its volume (lets say at a low speed), the kynetic energy of the gas molecules increases, what is ...
2
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1answer
118 views

Quantum ideal gas - Canonical ensemble - Occupation number summation notation (Huang)

(Question at the end, in bold, marked with an b)) For the quantum ideal gas, the hamiltonian (operator) of the system is: \begin{align} \mathcal H=\sum_{i=1}^N H_i=\sum_{i=1}^N \frac{P_i^2}{2m} ...
2
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2answers
40 views

Homework question about gas in a piston

What happens when the gas heats up? Is it possible to determine the amount of gas by the amount the piston moves? I think the "system" will move to the left (black arrow). Since pressure is defined ...
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2answers
204 views

Balloon gas temperature experiment in water

In this problem set I have a passage that describes an experiment that looks at the changing temperature as an air filled balloon rises to the surface from the bottom of a water filled tank. The graph ...
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0answers
32 views

Why does a balloon filled with air weigh more than an empty balloon [duplicate]

A common experiment to demonstrate that air has weight is to weigh a deflated balloon and an inflated one. The deflated balloon gives a lower reading on the balance and hence we conclude that air has ...
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2answers
99 views

Does QM needs refinement?

Suppose atoms of an ideal gas are represented by non overlapping wave function so that the system can be described classically. As time passes the packets spread. Therefore over a period of time we ...
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0answers
23 views

Barometric height formula for the mix of gases?

I am thinking on a problem which is an extesion of the wellknown barometric formula for a gas mixture. The main problem I can see, the curves describing the minimal energy (kinetic + gravitational) ...
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1answer
81 views

Pressure Question

I have a question that relates to an arrangement of natural gas pipelines but for simplicity I will be describing a less complex problem. Imagine that I have two large pressure vessels connected by a ...
8
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2answers
544 views

Where does the joules come from (ideal gas constant)?

I have not done any physics in ages and have recently started studying it. The first chapter in my book deals with the ideal gas constant: $$pV=nRT$$ It is rewritten as: $$R=\frac{pV}{nT}$$ When I ...
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1answer
203 views

What is the differential equation for pressure in a container with an orifice?

I've seen similar problems all over physics.SE and other sites. Most of the time it is about non-compressible fluids, or not about the differential equations. The physical system of interest is ...